[PATCH v3 1/4] mm: update the memmap stat before page is freed

Pasha Tatashin
2024-08-08T15:42:45Z

It is more logical to update the stat before the page is freed, to avoid
use after free scenarios.

Fixes: 15995a352474 ("mm: report per-page metadata information")
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
mm/hugetlb_vmemmap.c | 4 ++--
mm/page_ext.c | 8 ++++----
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 829112b0a914..fa83a7b38199 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -185,11 +185,11 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end,
static inline void free_vmemmap_page(struct page *page)
{
if (PageReserved(page)) {
- free_bootmem_page(page);
mod_node_page_state(page_pgdat(page), NR_MEMMAP_BOOT, -1);
+ free_bootmem_page(page);
} else {
- __free_page(page);
mod_node_page_state(page_pgdat(page), NR_MEMMAP, -1);
+ __free_page(page);
}
}

diff --git a/mm/page_ext.c b/mm/page_ext.c
index c191e490c401..962d45eee1f8 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -330,18 +330,18 @@ static void free_page_ext(void *addr)
if (is_vmalloc_addr(addr)) {
page = vmalloc_to_page(addr);
pgdat = page_pgdat(page);
+ mod_node_page_state(pgdat, NR_MEMMAP,
+ -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
vfree(addr);
} else {
page = virt_to_page(addr);
pgdat = page_pgdat(page);
+ mod_node_page_state(pgdat, NR_MEMMAP,
+ -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
BUG_ON(PageReserved(page));
kmemleak_free(addr);
free_pages_exact(addr, table_size);
}
-
- mod_node_page_state(pgdat, NR_MEMMAP,
- -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
-
}

static void __free_page_ext(unsigned long pfn)
--
2.46.0.76.ge559c4bf1a-goog